144 



Transactions of the Royal Society of South Africa. 



found at Ntimbankulu, Natal, for whicli the writer is indebted to Mr. H. C. 

 Burnup of Pietermaritzburg. 



The foot has well-marked peripodial grooves. The thin skin of the 

 mantle and visceral hump appears to be unpigmented, but the white 

 posterior aorta stands out conspicuously on the dark liver of the upper 

 whorls. 



The radula of a specimen from Ntimbankulu (text-fig. 11, B) measures 

 about -52 X -155 mm. when flattened out. The central and lateral teeth 

 are tricuspid with quadrate bases, the inner lateral teeth being almost 

 symmetrical and closely resembling the central teeth. Their mesocones 



B 



Text-fig. 11. — Trachycystis rudicostata Conn., Ntimbankulu, Natal. 



A. Anterior part of rcpi-oductive system ; X 25. 



B. Half of a transverse row of teeth from the radula ; X 1200. 



are long and rather narrow, although the cutting points are comparatively 

 short ; the ectocones and endocones are rather small. The marginal teeth 

 are more asymmetrical, with broader, shorter bases, and their endocones 

 and mesocones have longer points. The ectocones become split into two 

 very small cusps on the outer marginal teeth. The transverse rows of 

 teeth are straight in the middle, but tend to curve slightly forwards 

 in the region of the inner marginal teeth. The radular formula is : 

 (7+6+l + 6.+ 7)x80. 



The radula of a specimen from Vengo Mountain is very similar, although 

 the teeth are very slightly smaller, there being 97 transverse rows instead 

 of 80, notwithstanding that the radula is of about the same length as in the 

 specimen from Natal. 



It will be seen that the radula of this species is of the same general type 

 that is found in the larger species of Trachycystis. 



